Have 2 TIUs which I have been in the process of upgrading to version 5.
Have used the COM 4 port on a TIU to upload to version 5 software on both the TIU and a Remote successfully.
Completed update of two TIU units to Version 05.00. Verified version number for each TIU using the remote.
Note: My TIU version L unit permits downloads using either TIU serial port.